# Reaction between NaOH and Carbonic acid

I was presented with the following reaction when we were just learning about acids and bases:

$$\ce{2NaOH + H2CO3 -> H2O + Na2CO3}$$ however I had thought it might've been something like

$$\ce{NaOH + H2CO3 -> H2O + NaHCO3}$$

They both seem to fit the notion of a neutralization reaction creating a salt so how do I know that the first one is correct? The second reaction looks fine to me (is it that bicarbonate is too reactive?) and more intuitive as the carbonic acid just gives a proton away ending up as an ion to bond with $$Na$$, so how do I distinguish between these kind of cases?

This $$\ce{pH}$$ dependent equilibrium between carbonate and bicarbonate is one of the ways in which the blood $$\ce{pH}$$, and the $$\ce{pH}$$ of the mouth is maintained. It also helps aquatic life to survive in ocean waters. (Also see urea cycle and carbon cycle)
• @ AbhigyanC What about $\pu{pH}$ at the second equivalence point, more or less than 7? – Adnan AL-Amleh Jan 31 '19 at 15:35
• @AdnanAL-Amleh $\ce{pK_{a1}}$ and $\ce{pK_{a2}}$ of carbonic acid are $4.5\times10^{-7}$ and $4.7\times10^{-11}$, respectively. So it happens at $\ce{pH}=8.34$, using the formula for pH of a amphiprotic anion is the average of the two pK values. See chembuddy.com/… – Abhigyan Chattopadhyay Jan 31 '19 at 15:44